The current invention is generally related to data compression, and more particularly related to data compression technologies based upon signal activation relationships.
The entropy of signals is lowered by a conversion process that increases a certain signal series based upon the signal activation relationships. That is, subsequent to the above conversion of the information data, the initial information amount is compressed by entropy encoding. The compression effect is significant especially when a signal series containing a single signal frequently occurs. In addition, for a certain specific signal series, the information amount is further compressed by assigning an encoding word to the sequence. A prior art information conversion method of the above kind converts signals that exist after the second position from the beginning of a signal series that contains a single kind. For example, the prior art information conversion method such as xe2x80x9cmove-to-frontxe2x80x9d converts the signal into a certain predetermined signal such as 0. On the other hand, a post conversion signal varies for the front signal series containing a single kind. The post conversion signal depends upon a distance to a recent preceding equivalent signal or a number or kind of signals between the recent preceding equivalent signal and the current signal.
One exemplary conversion technique is disclosed in xe2x80x9cA locally adaptive data compression scheme,xe2x80x9d by Jon Louis Bentley, Daniel D. Sleator, Robert E. Tarjan and Victor K. Wei, Communication of the ACM, Vol. 29, No. 4, pp. 320-330, April (1986). The current signal is converted to a distance between the current signal and the recent preceding equivalent signal. The above distance assumes that the length of the repeated equivalent signal series is the length of the single signal.
Another prior art, Japanese Patent No. 2,722,665 discloses a bit rate reduction method. In the bit reduction method, a Huffman encoding word is generated based upon a combination of a most frequently repeated signal A and other signals that precede or proceed the signal A.
The above described Huffman encoding is generated for the signal series that have been converted based upon the signal activation relationships. In the combined use of the Huffman encoding and the signal activation based conversion, a Huffman encoding word is required to have each of the combinations of the signals A and the preceding signals. It is desirable to reduce the number of necessary Huffman encoding words that correspond to the combinations of prediction signals and other signals.
In order to solve the above and other problems, according to a first aspect of the current invention, a method of reducing a number of bits in data compression, including the steps of: converting repeated data in a signal sequence based upon a length between two of the repeated data, a number of the repeated data and a kind of the repeated data to generate converted data, the converted data having an activation sequence number k being referenced by tk; selecting a predetermined signal a; predicting a Group B that contains elements each representing the activation sequence number k for a portion of the converted data that contains none of the predetermined signal a, the portion of the converted data also having an inversely converted value that is equal to that of the predetermined signal a, the portion of the converted data being defined as a marking signal; comparing the activation sequence k to all of the converted data except for a portion containing the predetermined signal A the elements in the Group B to generate a comparison result; and assigning a predetermined encoding word to the corresponding portion of the converted data tk based upon the comparison result.
According to a second aspect of the current invention, a computer program including instructions for reducing a number of encoding words in data compression, including the tasks of: converting repeated data in a signal sequence based upon a length between two of the repeated data, a number of the repeated data and a kind of the repeated data to generate converted data, the converted data having an activation sequence k being referenced by tk; selecting a predetermined signal a; predicting a Group B that contains elements each representing the activation sequence number k for a portion of the converted data that contains none of the predetermined signal a, the portion of the converted data also having an inversely converted value that is equal to that of the predetermined signal a, the portion of the converted data being defined as a marking signal; comparing the position k to all of the converted data except for a portion containing the predetermined signal A the elements in the Group B to generate a comparison result; and assigning a predetermined encoding word to the corresponding portion of the converted data tk based upon the comparison result.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.